The invention relates to a fluid operated rotary drive comprising a drive housing and an output shaft able to be driven in relation to it by fluid force to perform a reciprocating rotary movement about its longitudinal axis and furthermore a pivotal abutment kinematically coupled with the output shaft and cooperating with at least one counter abutment extending into its path of pivoting for limiting the angular movement of the output shaft in an adjustable manner, said counter abutment being able to be positioned around the longitudinal axis of the output shaft in different abutment positions and able to be clamped in a releasable manner there against a clamping face of the housing, said clamping face extending at least for some distance about the longitudinal axis of the output shaft.
A rotary drive of this type as disclosed in the German patent publication DE 195 11 488 C2 comprises two counter abutments arranged in an adjustable fashion on an arcuate guide on the housing for a pivotal abutment rotationally locked with the output shaft. The counter abutments may be set in different abutment positions by clamping means along the outer periphery of the output shaft to set the angular position of the output shaft as is required. Owing to the clamping means a frictional connection with the drive housing is possible because the respective counter abutment may be held against a clamping face on the housing.
Normally the frictional locking of the counter abutments suffices to prevent undesired slipping out of the set abutment position. More especially in the case of security-related applications there is however a requirement for an even more reliable locking of the counter abutments offering an increased degree of security as regards slipping out of position.
The German patent publication DE 199 34 279 B4 discloses, in conjunction with a positioning abutment in linear drive, the provision of mutually complementary rack-like tooth means on the one hand on the housing and on the other hand on the respective abutment which are able to be meshed with each other in different positions. Though such gear tooth means may also be employed in a rotary drive—see for example the patent publication WO 99/14506 A1—owing to the curved shape necessary a great degree of complexity is involved. Furthermore the engagement of teeth means that there is no stepless positioning of the abutments.